Field Comparison of Two Instruments for Measuring Shell Deformation to Estimate Egg Shell Strength

A new technique for measuring shell deformation is described that improves the efficiency and precision of this test of egg shell strength. The time taken for the force applied to the egg to change a selected amount is accurately recorded. Since the constant rate of compression is known, the corresponding shell deformation can be calculated. Results show that shell deformation is independent of compression speed, but is significantly affected by introducing a hole in one compression surface. Results from the new instrument are comparable to readings from the apparatus of Schoorl and Boersma.